The present invention relates to a method and system for cleaning an ink jet printhead following a print operation. More particularly, the invention relates to a procedure wherein ink in the interior of the printhead is removed by air circulated under pressure through a printhead filled with a cleaning fluid.
An ink jet printer of the so-called "drop-on-demand" type has at least one printhead from which droplets of ink are directed towards a recording medium. Within the printhead, the ink may be contained in a plurality of channels and energy pulses are used to cause the droplets of ink to be expelled, as required, from orifices at the ends of the channels.
In a thermal ink jet printer, the energy pulses are usually produced by resistors, each located in a respective one of the channels, which are individually addressable by current pulses to heat and vaporize ink in the channels. As voltage is applied across a selected resistor, a vapor bubble grows in that particular channel and ink bulges from the channel orifice. At that stage, the bubble begins to collapse. The ink within the channel retracts and separates from the bulging ink which forms a droplet moving in a direction away from the channel orifice and towards the recording medium. The channel is then refilled by capillary action, which in turn draws ink from a supply container. Operation of a thermal ink jet printer is described in, for example, U.S. Pat. No. 4,849,774.
Commercial ink jet printers utilize a print cartridge comprising a printhead connected to an ink source via a manifold. The ink source is typically an ink bag or an ink tank or cartridge. At various times, it is desirable to clean the printhead following a print operation. It is known in the art to clean and reprime a printhead following a period of print operation. Typically, the printhead is mounted on a carriage which is periodically moved to a maintenance station where a cleaning mechanism engages the printhead to clean the printhead face and reprime the printhead.
U.S. Pat. No. 4,849,769 describes an ultrasonic cleaning method for removing particles from a printhead orifice plate. U.S. Pat. No. 5,210,550 discloses a maintenance station which primes a printhead and periodically stores the printhead in a humid environment
For some usages, it may be necessary to periodically provide a more thorough cleaning of the printhead including removal of ink from interior ink pathways (channels) and nozzles as well as the ink manifold. This thorough cleaning becomes a positive requirement when a printhead, following manufacture, is initially tested prior to shipping to a remote site. The printhead must be thoroughly cleaned following the print test and prior to shipping so as to remove ink that is still within the interior passageways and nozzles and any other particulate matter which could affect ink ejection and performance. From the above comments, it is necessary to clean a printhead outside of the conventional maintenance station. Known procedures are to manually introduce a flushing medium into the printhead manifold and flush the ink out through the nozzles. An automated cleaning method is disclosed in copending application U.S. Ser. No. 08/673,479 filed on Jul. 1, 1996, and assigned to the same assignee as the present invention. This reference describes a cleaning method wherein a water/gas mixture is forced into the printhead manifold and through the interior of the printhead, the mixture effectively flushing out residual ink within the printhead through the nozzles.
All of the references identified above are hereby incorporated by reference.
These methods are not completely effective and/or require complex cleaning systems.